This invention relates to a method and apparatus for producing perovskite compositions from precursor compositions using microwave heating in a crucible, capitalizing on the fact that perovskites are strong absorbers of microwaves and heat rapidly when irradiated with them.
"Perovskite" refers to a distorted orthorhombic crystal structure and to those complex oxide compositions such as LaCrO.sub.3 having that crystal structure. Perovskite compositions include the following: LaCrO.sub.3, LaMnO.sub.3, LaNiO.sub.3, LaCoO.sub.3, SrMnO.sub.3, LaFeO.sub.3, La.sub.1-x Sr.sub.x MnO.sub.3, La.sub.1-x Sr.sub.x CrO.sub.3, Y.sub.1-x Ca.sub.x CrO.sub.3, LaCr.sub.1-x Mg.sub.x O.sub.3, La.sub.1-x Ca.sub.x CrO.sub.3, CaTiO.sub.3, SrTiO.sub.3, Sr.sub.1-x La.sub.x TiO.sub.3, La.sub.x Sr.sub.1-x Cr.sub.y Mn.sub.1-y O.sub.3 (0&lt;x,y&lt;1) and others. High temperature 1-2-3 superconductors exhibit the perovskite structure. Particular applications for perovskite compositions include use in connection with chemical fuel cells, high temperature electrodes and chemical catalysis, and aerospace applications.
Perovskite compositions have been produced by heating stoichiometric mixtures of the precursors, but conventional methods are costly in terms of equipment, energy and processing time. They typically employ furnace temperatures in the range of from about 1250.degree. C. to about 1475.degree. C. for time periods ranging from about 11 hours to about 48 hours.